­Because food is so important to survival, food preservation is one of the oldest technologies used by human beings. In this article, we'll look at all of the different preservation techniques commonly used today, including:

Refrigeration and freezing

Canning

Irradiation

Dehydration

Freeze-drying

Salting

Pickling

Pasteurizing

Fermentation

Carbonation

Cheese-making

Chemical preservation

The basic idea behind all forms of food preservation is either:

To slow down the activity of disease-causing bacteria

To kill the bacteria altogether

I­n certain cases, a preservation technique may also destroy enzymes naturally found in a food that cause it to spoil or discolor quickly. An enzyme is a special protein that acts as a catalyst for a chemical reaction, and enzymes are fairly fragile. By increasing the temperature of food to about 150 degrees Fahrenheit (66 degrees Celsius), enzymes are destroyed.

A food that is sterile contains no bacteria. Unless sterilized and sealed, all food contains bacteria. For example, bacteria naturally living in milk will spoil the milk in two or three hours if the milk is left out on the kitchen counter at room temperature. By putting the milk in the refrigerator you don't eliminate the bacteria already there, but you do slow down the bacteria enough that the milk will stay fresh for a week or two.

Let's look at all of the different forms of food preservation in detail.

Edison, Bell, the Wright Brothers -- sure, their inventions changed the world, but they didn't tend to think up much for the kids. But that doesn't mean there haven't been some good ones over the years. So pick up your pogo stick and hop along to find out five of our favorites.